Determining safety risk using natural language processing

ABSTRACT

A network system coordinates users who provide geographical location-based services to users. Users can provide textual feedback regarding the services provided by other users. To create a safe user experience and encourage users to continue using the services, the network system determines safety risks of the users by analyzing the textual feedback from users along with metadata associated with the textual feedback. For example, the network system determines a safety score for a user based on classifying textual feedback according to different types of safety risk related to topics such as vehicle operation or interpersonal behavior. The network system can train classifiers using feature vectors derived from textual feedback previously received from users of the network system, which may be labeled in a supervised training process. The network system may provide interventions to high-risk users to help mitigate their safety risk and prevent safety incidents from occurring.

BACKGROUND 1. Field of Art

The present disclosure generally relates to determining safety risks ofusers of a network system, and more specifically to using naturallanguage processing and various types of classifiers to determine thesafety risks.

2. Description of the Related Art

Natural language processing techniques can be used to determinecharacteristics of a string of text. For example, a sentence includingthe words “cats” and “dogs” is likely to be relevant to the topic ofpets. However, the sentence “it's raining cats and dogs” includes bothof those words, but is not relevant to the topic of pets. Instead, thesentence refers to an English idiom. Thus, it is challenging todetermine the topic of a sample of text due variations in context.

In a system, providers provide services to users, for example, theprovider uses a vehicle to transport the user for a trip. If the usersperceive the providers as unsafe (e.g., driving recklessly or beingconfrontational), the users may stop using the system's services. Userscan provide textual feedback to the system to report incidences ofunsafe behavior, but automatic and systematic analysis of this textualfeedback to determine provider characteristics and level of safety riskshas proven challenging. Without such an automated way, subjective humantechniques may be applied that are expensive to implement and rely onthe subjective considerations of individual reviewers. It would bedesirable for the system to automatically analyze the textual feedbackto determine whether providers are safe or unsafe, and for the system tohandle submissions of the textual feedback at a large scale.

SUMMARY

In one embodiment, a method comprises receiving, by a network systemfrom a client device of a user, textual feedback associated withmetadata and a provider. The textual feedback includes a set of words.The metadata describes the contexts of the textual feedback. The networksystem determines a feature vector for the textual feedback bycharacterizing the set of words and the metadata. There are multiplesubcategories of safety risk. The network system determines a firstsafety sub-score by applying the feature vector to a first classifierassociated with a first subcategory of safety risk. The network systemdetermines a second safety sub-score by applying the feature vector to asecond classifier associated with a second subcategory of safety riskdifferent than the first subcategory of safety risk. After determiningsub-scores for all subcategories, the network system determines anoverall safety score for the provider using another classifier based, atleast in part, on the safety sub-scores.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a system environment for a network systemaccording to one embodiment.

FIG. 2 is a block diagram illustrating the architecture of the networksystem according to one embodiment.

FIG. 3A is a data flow diagram for preparing training data according toone embodiment.

FIG. 3B is a diagram of feature vectors in latent dimension spaceaccording to one embodiment.

FIG. 3C is a diagram comparing the similarity of feature vectors inlatent dimension space according to one embodiment.

FIG. 4A is a data flow diagram for training classifiers according to oneembodiment.

FIG. 4B is a data flow diagram for using the trained classifiers shownin FIG. 4B to determine a safety score according to one embodiment.

FIG. 5 is a flowchart illustrating a process for determining safetyscores according to one embodiment.

FIG. 6 is a high-level block diagram illustrating physical components ofa computer used as part or all of the components from FIG. 1, accordingto one embodiment.

The figures depict embodiments of the present invention for purposes ofillustration only. One skilled in the art will readily recognize fromthe following discussion that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles of the invention described herein.

DETAILED DESCRIPTION

A network system coordinates providers who provide geographicallocation-based services to users. The location-based services mayinclude transportation of users in a vehicle. Users can provide textualfeedback regarding the services provided by the providers. To create asafe user experience and encourage users to continue using the services,the network system determines safety risks of the providers by analyzingthe textual feedback from users along with metadata associated with thetextual feedback. For example, the network system determines a safetyscore for a provider based on classifying textual feedback according todifferent types of safety risk related to topics such as vehicleoperation or interpersonal behavior. Each safety risk classifier maygenerate its own score representing a level of risk related to thecorresponding type of safety risk. The individual scores may be combinedwith the metadata by an ensemble classifier to determine the likelihoodof an overall safety risk of a provider. The network system may provideinterventions to high-risk providers to help mitigate their safety riskand prevent safety incidents from occurring.

I. System Overview

FIG. 1 is a diagram of a system environment for a network system 100according to one embodiment. Users of the network system 100 may includeproviders that provide service to other users. In an example use case, aprovider operates a vehicle to transport a user from a first location(e.g., an origin or pickup location) to a second location (e.g., adrop-off location). Other types of service include, for example,delivery of goods such as mail, packages, or consumable items.

The system environment includes the network system 100 and one or moreclient devices 110 of users of the network system 100, for example,client device 110A of a user and client device 110B of a providerproviding service to the user, which may collectively be referred toherein as a “client device 110” or “client devices 110.” The varioussystems shown in FIG. 1 are connected to each other via a network 130.In other embodiments, different and/or additional entities can beincluded in the system architecture. The functions performed by thevarious entities of FIG. 1 may vary in different embodiments. Thenetwork system 100 determines safety risks of providers based onfeedback from users.

A user can interact with the network system 100 through the clientdevice 110, e.g., to request transportation or to receive requests toprovide transportation. A client device 110 can be a personal or mobilecomputing device, such as a smartphone, a tablet, or a notebookcomputer. In some embodiments, the client device 110 executes a clientapplication that uses an application programming interface (API) tocommunicate with the network system 100 through the network 130. Theclient application of the client device can present information receivedfrom the network system 100 on a user interface, such as a map of thegeographic region and the current location of the client device 110. Theclient application running on the client device 110 can determine thecurrent location using a location sensor of the client device 110, suchas a global positioning system (GPS) receiver, and provide the currentlocation to the network system 100.

In one embodiment, through operation of the client device 110, a usermakes a trip request to the network system 100. For example, the triprequest may include user identification information, the number ofpassengers for the trip, a requested type of the service provider (e.g.,a vehicle type or service option identifier), the current locationand/or the origin location (e.g., a user-specific geographical locationfor pickup, or a current geographical location of the client device110), and/or the destination for the trip. The user may also inputfeedback via a user interface of the client device 110. For example, theuser inputs textual feedback using a touchscreen keyboard of the clientdevice 110. Depending on implementation, before, during, or after thetrip, the client device 110 can provide the feedback to the networksystem 100.

In some embodiments, a provider uses a client device 110 to interactwith the network system 100 and receive invitations to provide servicefor users. For example, the provider is a person operating a vehiclecapable of transporting users. In some embodiments, the provider is anautonomous vehicle that receives routing instructions from the networksystem 100. For convenience, this disclosure generally uses a car as thevehicle, which is operated by a driver as an example provider. However,the embodiments described herein may be adapted for a provider operatingalternative vehicles (e.g., boat, airplane, helicopter, etc.) orvehicles that do not necessarily need to be operated by a person.

In some embodiments, a provider can receive invitations or assignmentrequests through a client device 110. An assignment request identifies auser who submitted a trip request to the network system 100 anddetermines the origin location and/or the destination location of theuser for a trip. For example, the network system 100 can receive a triprequest from a client device of a user, select a service provider from apool of available (or “open”) providers to provide the trip, e.g., basedon the vehicle type, determined origin location, and/or the destinationlocation. The network system 100 transmits an assignment request to theselected provider's client device 110.

Client devices 110 can communicate with the network system 100 via thenetwork 130, which may comprise any combination of local area and widearea networks employing wired or wireless communication links. In oneembodiment, the network 130 uses standard communications technologiesand Internet protocols. For example, the network 130 includescommunication links using technologies such as the Internet, 3G, 4G,BLUETOOTH®, or WiFi. In some embodiments, all or some of thecommunication links of the network 130 may be encrypted.

The client devices 110 may provide textual feedback, in response to userinput, as safety tickets to the network system 100. For example, asafety ticket includes a user's feedback that describes a provider'sunsafe vehicle operation during a service. It is challenging to processall of the textual feedback manually at large scale. However, thenetwork system 100 can automatically analyze the textual feedback todetermine whether providers are safe or unsafe. In particular, thenetwork system 100 may use various classifiers to determine safety risksof providers.

II. Example System Architecture

FIG. 2 is a block diagram illustrating the architecture of a networksystem 100 according to one embodiment. The network system 100 includesa matching engine 200, map data store 205, user data store 210, feedbackengine 220, feedback data store 225, machine learning engine 230, andtraining data store 235. In other embodiments, the network system 100may include additional, fewer, or different components for variousapplications. Conventional components such as network interfaces,security functions, load balancers, failover servers, management andnetwork operations consoles, and the like are not shown as to notobscure the details of the system architecture.

In some embodiments, users and/or providers use their client devices 110to register with the network system 100, for example, by creatingaccounts and providing user information (e.g., contact information, ahome or office address, or billing information) to the network system100. The network system 100 stores the user information in the user datastore 210. The network system 100 can associate feedback received from auser or data from trips taken by the user with the registered account ofthe user and/or the provider.

The matching engine 200 selects providers to service the requests ofusers. For example, the matching engine 200 receives a trip request froma user and determines a set of candidate providers that are online, open(e.g., are available to transport a user), and near the requested origin(pickup) location for the user, e.g., based on map information from adata source. The matching engine 200 selects a provider from the set ofcandidate providers to which it transmits an assignment request. Theprovider can be selected based on the provider's location, the originand/or destination location, the type of the provider, the amount oftime the provider has been waiting for an assignment request and/or thedestination of the trip, among other factors.

The map data store 205 stores map information of geographic regions inwhich the network system 100 offers services such as transportation forusers. The map information may include map properties of a geographicalregion such as road properties that describe characteristics of the roadsegments, such as speed limits, road directionality (e.g., one-way ortwo-way), traffic history, traffic conditions, addresses on the roadsegment, length of the road segment, and type of the road segment (e.g.,surface street, residential, highway, toll). The map properties also caninclude properties about intersections, such as turn restrictions, lighttiming information, throughput, and connecting road segments.

The feedback engine 220 receives feedback from client devices 110 of auser of the network system 100. According to examples, feedback data fora trip can include or be associated with textual feedback, a rating orscore (e.g., a number of stars out of five stars), an identifier of theuser, an identifier of the provider, an identifier of the request orservice, or other user-specified content (e.g., a selection of optionsor criteria the user liked or disliked). In some embodiments, thefeedback engine 220 converts non-textual feedback into a textualfeedback for further processing. For example, feedback indicating asentiment may be converted into “satisfied,” “unsatisfied,” “negative,”“neutral,” or “positive.” As another example, the feedback engine 220uses speech-to-text algorithms to convert audio feedback recorded by anaudio sensor of the client device 110 into textual feedback.Additionally, the feedback engine 220 may use image-processingtechniques to identify one or more objects shown in a photo captured bya camera of client device 110 of a user, and determine textual feedbackassociated with the identified objects. For example, the feedback engine220 determines text representing the license plate number from a photoof the license plate.

The feedback engine 220 can receive metadata associated with feedback.Metadata describes context of feedback not necessarily provided by textincluded in the feedback. For example, the metadata is based onhistorical actions of a user or provider of the network system 100 suchas a number of services that the user has received from providers orthat the provider has provided to users for a given duration of time, anumber of incidents that occurred during the services, or certaincategories of safety risk associated with the incidents (e.g., which maybe retrieved from the user data store 210).

In other examples, the metadata is based on information for a particularservice. For instance, for a particular trip, the metadata indicates thetrip duration or distance traveled, the origin or destination locationof the trip, the location of a client device 110 when feedback wassubmitted, or telematics data captured by a client device 110 of theuser or provider during the trip. Metadata may be associated withinteractions performed for a service, for example, whether the usercommunicated with a provider during a trip (e.g., to determine a pick uplocation for the user to meet with the provider), or whether the usercommunicated with personnel of the network system 100 (e.g., because theuser experienced difficulties to request the service or during theprovided service). Metadata may describe information regarding thesubmission of the textual feedback. For example, the metadata indicateswhether the textual feedback was submitted by a user or provider, or asubmission channel (e.g., email, text message, user interface button, orclient application).

The feedback engine 220 analyzes textual feedback received from users togenerate feature vectors that characterize the textual feedback. Forinstance, the feature vectors quantize the linguistic context of wordsincluded in the textual feedback. Additionally, the feature vectorsrepresent the textual feedback using any number of dimensions in latentdimension space. Thus, feature vectors of textual feedback having wordswith similar linguistic context will be closer to each other in thelatent dimension space. Comparison of feature vectors is furtherdescribed below with reference to FIGS. 3A-B. The feedback engine 220may store feature vectors and other types of training data in thetraining data store 235. The training data store 235 may include the mapdata store 205, user data store 210, and/or feedback data store 225, insome embodiments.

To generate the feature vectors, the feedback engine 220 may usedifferent types of statistical models and natural language processing(NLP) techniques, for example, lexical analysis, syntactic analysis,semantic analysis, synonyms, bag-of-words, information retrieval,sentiment analysis, stemming, fuzzy matching, anaphora resolution,word2vec (e.g., latent vector embedding), linear discriminant analysis(LDA), and/or other types of topic modeling features. The feedbackengine 220 identifies words and phrases included in textual feedback bydetermining a number of n-grams of the textual feedback. The n-grams maybe determined based on an identified language of the textual feedback(e.g., English, Chinese, Spanish, etc.). The feedback engine 220 canalso generate feature vectors that characterize metadata associated withthe textual feedback. Unlike textual feedback that may be languagedependent, metadata may be independent across different languages.

The feedback engine 220 uses information retrieval techniques such asdetermining a term frequency-inverse document frequency (TF-IDF) for aword or phrase in textual feedback, in some embodiments. Generally, aword that occurs more frequently in textual feedback is more relevant tothe topic of the textual feedback. For example, if textual feedbackincludes five occurrences of the word “speeding” and one occurrence ofthe word “office,” then the data source is more likely relevant tospeeding, rather than to an office. However, words includingconjunctions such as “and”, “but”, and “or,” as well as antecedents suchas “a” and “the” typically occur frequently in textual feedbackregardless of the topic. To account for these types of words, a TF-IDFtechnique considers the occurrence of these words in a corpus, e.g., alarge collection of textual feedback or types of textual documents. Asan example, for a given textual feedback, the feedback engine 220determines the relevance for a word based on comparing the number ofoccurrences of the word in the given textual feedback with anothernumber of occurrences of the word in the corpus.

The feedback engine 220 can determine linguistic context based on theoccurrence of a particular combination of two or more words in textualfeedback. As an example, the word “swerving” can occur in textualfeedback, such as “the car was swerving on the snowy road” or “thedriver was not familiar with the roads so we were swerving around,” andthe word “drunk” can occur in textual feedback, such as “my friend wasdrunk so I helped her home” or “I lost my keys since I was so drunk.” Ina collection of textual feedback, the word “swerving” can occur onaverage 0.1 times per textual feedback and the word “drunk” can occur onaverage 0.05 times per textual feedback. Additionally, the words“swerving” and “drunk” can occur together on average 0.001 times pertextual feedback. Because the likelihood of these two words occurringtogether is much less (e.g., by at least an order of magnitude) than thelikelihood of each word occurring individually per textual feedback, thefeedback engine 220 determines that the combined occurrence is a strongindicator of a topic of the textual feedback.

Following in the example above, the feedback engine 220 determines thata sample textual feedback “the driver was swerving a lot and I think hehis driving too fast” is likely relevant to the topic of aggressivedriving. Accordingly, a feature vector characterizing the sample textualfeedback generated by the feedback engine 220 will indicate that thecontext of the sample textual feedback is strongly matches the topic ofaggressive driving. For instance, if the feature vector uses numericalvalues to represent latent space dimensions each associated with atopic, the dimension corresponding to the topic of aggressive drivingwill have greater magnitude value than that of other dimensionscorresponding to topics such as “friendly personality” or “physicalaltercation.”

In some embodiments, the feedback engine 220 generates feature vectorscharacterizing a series of textual feedback, along with any suitablemetadata associated with the textual feedback. For instance, in responseto receiving the sample textual feedback “the driver was swerving a lotand I think he his driving too fast,” the network system 100 provides amessage (e.g., for display on a client device 110) to the usersubmitting the sample textual feedback asking the question “About whatis the average speed of the vehicle?” In response to the question, theuser submits the follow-up textual feedback “80 miles per hour” or “80mph.” Thus, the resulting feature vector characterizes the sampletextual feedback, the message with the question, and the follow-uptextual feedback. The metadata may include telematics data capturedusing the user's client device 110 indicating that the driver washarshly accelerating and braking.

As another example of how the feedback engine 220 can determinelinguistic context based on semantic analysis of two or more words, thefeedback engine 220 determines that the textual feedback “he hit me withhis hand and it hurt” is related to the topic of “physical altercation.”An example textual feedback including the word “hit” is “the driver'smusic hit the spot,” an example textual feedback including the word“hand” is “he gave me a hand with my grocery bags,” and an exampletextual feedback including the word “hurt” is “my feet hurt so much fromwalking—glad I got a ride!” Each of these three example textual feedbackare not related to the topic of “physical altercation.” However, thefeedback engine 220 determines that the occurrence of each of the words“hit,” “hand,” and “hurt” in the same sentence strongly indicates thatthe textual feedback including that sentence is likely related to thetopic of “physical altercation.” Thus, the feedback engine 220 can usesemantic analysis to avoid false positives that may occur when analyzingwords individually without linguistic context.

The machine learning engine 230 determines safety scores for providersof network system 100 using different types of classifiers. Using thefeature vectors generated by the feedback engine 220 to characterizetextual feedback and/or associated metadata, the machine learning engine230 trains classifiers having different types of safety risk (e.g.,“vehicle operation” or “interpersonal behavior”). The machine learningengine 230 may implement machine learning techniques such as deeplearning, logistic regression with L1 penalty (L1 regularization) or L2penalty (L2 regularization), convolutional neural networks, or othertypes of dimensionality reduction processes. The classifiers generatesafety sub-scores, which are aggregated as an input to an “ensembleclassifier” that determines a safety score based on each of the safetysub-scores for a given provider and/or metadata.

Based on the safety score, the ensemble classifier may determine whetherthe provider has a “low,” “medium,” or “high” safety risk. In an exampleuse case where the safety score is represented by a percentage value, asafety score under 50% is “low,” a safety score from 50% to 90% is“medium,” and a safety score 90% and greater is “high.” If the ensembleclassifier determines that the provider has a “high” safety risk, thenetwork system 100 may take action to mitigate the safety risk andprevent future safety incidences from occurring. For example, thenetwork system 100 communicates a warning message via a client device110 of the provider, or suspends the account of the provider for acertain duration of time, or notifies an administrator of the networksystem 100 to further review the provider and the feedback.

In other embodiments, the ensemble classifier determines a binary output(which may be based on the safety score), for instance, whether theprovider is safe or not safe. In some embodiments, the ensembleclassifier determines that a provider is not safe in response todetermining that one or more of the safety sub-scores is greater than athreshold value. For example, even if the provider has a “low” safetysub-score for “vehicle operation,” if the provider has a “high” safetysub-score for “interpersonal behavior” greater than the threshold value,the ensemble classifier may determine that the provider is unsafe. Themachine learning engine 230 can train the ensemble classifier or otherclassifiers using information describing false positives and falsenegatives determined based on manual input. For example, a falsepositive occurs when the ensemble classifier determines that a provideris not safe, though the provider is actually safe; a false negativeoccurs when the ensemble classifier determines that a provider is safe,though the provider is actually not safe.

In other examples, the ensemble classifier learns a weighting or otherrelationship between each type of the safety sub-scores to learn anddetermine which combinations of sub-scores generate a sufficient overallsafety score. In addition to the safety sub-scores, the ensembleclassifier may also incorporate the metadata associated with thefeedback to learn a relationship between the metadata, the sub-scores,and outcome safety score as discussed further herein.

III. Example Feature Vectors

FIG. 3A is a data flow diagram 300 for preparing training data accordingto one embodiment. In this example, the training data may be supervisedtraining data labeled manually, though in other examples the trainingdata may be automatically labeled. The network system 100 receivestextual feedback from users and providers. The network system 100provides the textual feedback to one or more third party systems toconduct a crowdsourcing audit. A third party system may be acrowdsourcing Internet marketplace such as a Mechanical Turk, whichassigns textual feedback to crowdsourcing workers (e.g., humans) whodetermine which textual feedback should be considered for preparingtraining data. For instance, the crowdsourcing workers filter outtextual feedbacks that are incomplete or faulty submissions, spam,redundant, or otherwise indicative of poor quality. Additionally, thecrowdsourcing workers filter out textual feedback that are determined tobe unrelated to safety risk, e.g., “driver was so late,” “the car had aweird smell,” or “wish the driver had free water.”

The network system 100 conducts an internal audit of the filtered set oftextual feedback. The internal audit may be conducted by personnel ofthe network system 100 and thus, provide another level for filtering outtextual feedback that are not useful for training classifiers fordetermining safety risk. In some embodiments, the crowdsourcing auditconducts a “coarse filter,” while the internal audit conducts a “finefilter.” In other words, the personnel of the network system 100 usemore strict rules or criteria, relative to those used by thecrowdsourcing workers, to determine which textual feedback to exclude orinclude in a filtered set. Further, the network system 100 performs the“coarse filter” before the “fine filter” because the personnel of thenetwork system 100 may require more resources than do the crowdsourcingworkers, in some embodiments.

Based on analysis of textual feedback in a filtered set, the personnelof the network system 100 determine whether to associate the textualfeedback with a safety label. If so, the personnel determine a categoryof safety risk for the textual feedback. For example, the filtered setof textual feedback includes “driver was speeding” and “he did not obeytraffic signs” labeled with the category of “vehicle operation” safetyrisk, as well as “rude driver” and “I wish she was friendlier” labeledwith the category of “interpersonal behavior” safety risk. A textualfeedback may be labeled with more than one category of safety risk. Thefeedback engine 220 can store the labeled textual feedback in thetraining data store 235. The feedback engine 220 generates featurevectors to characterize these four example textual feedback, which arefurther described below.

FIG. 3B is a diagram 310 of feature vectors in latent dimension spaceaccording to one embodiment. The example diagram 310 shown in FIG. 3Aincludes two dimensions for purposes of illustration, though inpractice, the latent dimension space includes any number of dimensions(e.g., hundreds or thousands). Referring to the example described inFIG. 3A, the feedback engine 220 generates feature vector A and featurevector B to characterize the textual feedbacks “driver was speeding” and“he did not obey traffic signs,” respectively. The feedback engine 220generates feature vector C and feature vector D to characterize thetextual feedbacks “rude driver” and “I wish she was friendlier,”respectively. Relative to feature vectors C and D, feature vector A ismore closely resembles feature vector B because the textual feedback“driver was speeding” is linguistically more similar to “he did not obeytraffic signs,” in comparison to “rude driver” and “I wish she wasfriendlier.”

As an example, dimension 1 is correlated with words having linguisticcontext describing respectful interpersonal behavior. Since the textualfeedback characterized by feature vectors C and D are indicative ofdisrespectful interpersonal behavior, feature vectors C and D havenegative values in dimension 1. Additionally, dimension 2 is correlatedwith words having linguistic context of dangerous vehicle operation.Since the textual feedback characterized by feature vectors A and B areindicative of dangerous driving, feature vectors A and B have positivevalues in dimension 2. In some embodiments, the feedback engine 220generates feature vectors that also characterize metadata in one or moredimensions.

The machine learning engine 230 trains a first classifier associatedwith the “vehicle operation” category of safety risk using featurevectors A and B, which are labeled with the same category of safetyrisk. The first classifier generates a “vehicle operation featurevector” based on feature vectors A and B, for example, a weightedaverage of feature vectors A and B. Similarly, using feature vectors Cand D, the machine learning engine 230 trains a second classifierassociated “interpersonal behavior” category of safety risk, whichdetermines an “interpersonal behavior feature vector” based on featurevectors C and D. In some embodiments, the machine learning engine 230can consolidate different categories of safety risk. For example, themachine learning engine 230 trains a classifier associated with a“altercation” category of safety risk using feature vectorscharacterizing textual feedback such as “he hit me,” (an example ofphysical altercation) and “she was swearing” (an example of verbalaltercation).

FIG. 3C is a diagram 320 comparing the similarity of feature vectors inlatent dimension space according to one embodiment. The diagram 320includes the “vehicle operation feature vector” and the “interpersonalbehavior feature vector” in the latent dimension space as shown in FIG.3B. The machine learning engine 230 can train classifiers to determinesafety sub-scores associated with different categories of safety risk.For instance, a given classifier synthesizes feature vectors to predicta safety sub-score for a given subcategory of safety risk, where thesafety sub-score denotes a confidence level that classified tickets(e.g., textual feedback) belong to the given subcategory of safety risk.The classifiers may include linear type classifiers or non-linear typeclassifiers (e.g., based on decision-trees). In some embodiments such asthe example shown in FIG. 3C, the classifiers may determine safetysub-scores based on the cosine similarity between two or more featurevectors.

As an example use case, the network system 100 receives the sampletextual feedback “when I told the driver he was driving too slow, heyelled and then ignored me.” The feedback engine 220 generates featurevector E to characterize the sample textual feedback. The linguisticcontent of the sample textual feedback includes the phrase “driving tooslow” that is related to vehicle operation, as well as the phrases “heyelled” and “ignored me” that are related to interpersonal behavior.Based on a one-to-one feature vector comparison, feature vector E doesnot closely resemble either the vehicle operation feature vector or theinterpersonal behavior feature vector because feature vector E includeslinguistic content related to both of the associated categories ofsafety risk. Rather, feature vector E represents an aggregate (e.g.,weighted average or sum) of the vehicle operation feature vector and theinterpersonal behavior feature vector, in the example shown in FIG. 3C.An ensemble classifier, which is further described below, can analyzevarious feature vectors collectively (e.g., using feature vector E),rather than using a one-to-one feature vector comparison, to determinesafety risk levels that account for different types of potential safetyrisk in some embodiments.

To evaluate feature vector E with respect to the different safetysub-scores, the feedback engine 220 applies feature vector E to thefirst classifier (associated with the “vehicle operation” category ofsafety risk), which in one embodiment, determines a first safetysub-score based on the cosine similarity angle 330. In addition, thefeedback engine 220 applies the feature vector E to the secondclassifier (associated with the “interpersonal behavior” category ofsafety risk), which in one embodiment, determines a second safetysub-score based on the cosine similarity angle 340. In otherembodiments, classifiers can determine safety sub-scores using otherstatistical models such as information entropy, decision tree, Pearson'scorrelation, or linear least squares.

IV. Example Safety Risk Classifiers

IV. A. Training Classifiers

FIG. 4A is a data flow diagram 410 for training classifiers according toone embodiment. In “training stack 1,” the machine learning engine 230trains multiple classifiers each associated with different categories ofsafety risk. Referring to the example previously described withreference to FIG. 3A-C, the machine learning engine 230 trains a vehicleoperation classifier 420 using feature vectors A and B, and trains aninterpersonal behavior classifier 430 using feature vectors C and D. Thevehicle operation classifier 420 determines safety “sub-score A” and theinterpersonal behavior classifier 430 determines safety “sub-score B.”Other categories of safety risk include “physical altercation,”“language,” “sexual harassment,” or “uncomfortable environment,” whichmay be associated with classifiers determining safety sub-scores for thecorresponding category of safety risk. As discussed above, these trainedclassifiers may learn a feature vector for each sub-score, or may learna score based on the feature vectors without representing the sub-scorein the feature vector space, e.g., as shown in FIG. 3B. In someembodiments, “training stack 1” includes one or more classifiersassociated with metadata rather than a category of safety risk.Classifiers associated with metadata may generate sub-scores based oninput metadata of textual feedback.

In “training stack 2,” the machine learning engine 230 trains anensemble classifier 450 using safety sub-scores determined in “trainingstack 1.” In some embodiments, the machine learning engine 230 alsotrains the ensemble classifier 450 using metadata associated withtextual feedback used to derive feature vectors to train the classifiersin “training stack 1.” Thus, the machine learning engine 230 can applythe metadata for training in both “training stack 1” and “training stack2.”

IV. B. Determining Safety Risk Using Trained Classifiers

FIG. 4B is a data flow diagram 440 for using the trained classifiersshown in FIG. 4B to determine a safety score according to oneembodiment. Referring to the previous example, the feedback engine 220generates feature vector E to characterize the sample textual feedback“when I told the driver he was driving too slow, he yelled and thenignored me” received from a user and metadata associated with the sampletextual feedback. For instance, the metadata indicates that a tripprovided by the provider (e.g., the driver) for the user had a durationof one hour. Additionally, the metadata includes telematics dataindicating the average speed of the provider's vehicle transporting theuser, as well as harsh braking and accelerations, during differentsegments of the trip.

The machine learning engine 230 applies feature vector E to the vehicleoperation classifier 420 and the interpersonal behavior classifier 430,which determine safety sub-scores C and D, respectively. The machinelearning engine 230 applies safety sub-scores C and D, along with themetadata, to the ensemble classifier 450, which determines a safetyscore for the provider who is described by the sample textual feedback.The ensemble classifier may determine the safety score by aggregatingthe safety sub-scores C and D, which can be weighted differently.

In one use case, the safety sub-scores C and D are 50% and 60%,respectively. A greater percentage indicates a greater likelihood thatthe provider has a safety risk of the corresponding category, forinstance. As one example, the ensemble classifier 450 applies a 10%weight to boost safety sub-score C from 50% to 55%, e.g., because theensemble classifier 450 learns during training that dangerous vehicleoperation is a greater safety risk than poor interpersonal behavior. Inone example, the ensemble classifier 450 sums 55% and 60% to determinethe safety score of 115% for the provider. In other examples, theensemble classifier 450 learns a weighing for each of the sub-scores tocombine the sub-scores without directly boosting a sub-score. As anotherexample, the ensemble classifier 450 may learn a combination functionfor the safety sub-scores to determine the safety score without directlyweighing or boosting the likely safety risk of each sub-score. Forexample, the ensemble classifier 450 may learn a function (e.g., througha decision tree, learned network, and/or other learned model) thatcombines safety sub-scores to generate a resulting safety score in therange of 0% to 100%. In other embodiments, safety sub-scores and safetyscores may be represented in formats other than percentage values.

The safety score can also be determined based on the associatedmetadata, in some embodiments. As an example using metadata, theensemble classifier 450 may compare the duration of the trip withreference durations of other sample trips similar to the trip of theuser (e.g., information about trips taken by other users of the networksystem 100 retrieved from the user data store 210). These comparisonsmay be used to generate the features describing the metadata for theclassifier. The ensemble classifier 450 determines that the duration ofthe trip is greater (e.g., by one standard deviation) than the averageof the reference durations, which is consistent with the sentiment“driving too slow” from the sample textual feedback. Further, theensemble classifier 450 determines that the average speed of the vehicleindicated by the telematics data is 40 miles per hour (mph) for a givensegment of the trip. Based on map information from the map data store205, the ensemble classifier 450 determines that the user was travelingon a freeway having a 65 mph speed limit during the given segment. Inresponse to determining that the difference between the 65 mph speedlimit and the average speed of 40 mph is greater than a threshold value,the ensemble classifier 450 can verify that the provider was “drivingtoo slow.” The ensemble classifier 450 may increase the safety score ifthe metadata is consistent with the linguistic context of the associatedtextual feedback. On the other hand, if the metadata is inconsistentwith the linguistic context, the ensemble classifier 450 may decreasethe safety score. In other words, the ensemble classifier 450 can usethe metadata to verify the veracity of words and phrases in textualfeedback.

As additional examples of metadata analysis, the ensemble classifier 450may increase safety scores (more safety risk) if the provider has anumber of past incidences greater than a threshold number or if the tripwas provided during the night time. These characteristics of theprovider's prior activity may be included in the metadata. The ensembleclassifier 450 can determine that certain metadata is applicable to aclassifier of a particular category of safety risk. For instance, a longduration of a trip indicates a greater likelihood that the provider wasinvolved in a traffic accident during the trip, and thus the ensembleclassifier 450 increases a weight for a safety sub-score of a classifierhaving an “accident” category of safety risk. The relationship betweenthese types of metadata and safety sub-scores may be specified in thedesign of the ensemble classifier 450. Alternatively, the ensembleclassifier 450 may learn the relationship of such types of metadata andsafety sub-scores through training of the ensemble classifier 450. Theensemble classifier 450 may also identify certain routes that have agreater number of safety incidents (e.g., traffic collisions or speedingviolations) based on map information from the map data store 205. Theensemble classifier 450 may decrease safety scores (less safety risk) ifthe provider has previously provided a number of services to usersgreater than a threshold number or if the trip was provided during thedaytime.

V. Example Process Flow

FIG. 5 is a flowchart illustrating a process 500 for determining safetyscores according to one embodiment. In some embodiments, the process 500is used by the network system 100 within the system environment inFIG. 1. The process 500 may include different or additional steps thanthose described in conjunction with FIG. 5 in some embodiments orperform steps in different orders than the order described inconjunction with FIG. 5.

In one embodiment, the feedback engine 220 receives 510 textual feedbackassociated with metadata from a client device 110 of a user of thenetwork system 100. The user inputs textual feedback for a provider,where the user receives service from the provider. The feedback engine220 determines 520 a feature vector for the textual feedback bycharacterizing words of the textual feedback and the metadata. Themachine learning engine 230 determines 530 a first safety sub-score byapplying the feature vector to a first classifier associated with afirst category of safety risk (e.g., “vehicle operation”). The machinelearning engine 230 determines 540 a second safety sub-score by applyingthe feature vector to a second classifier associated with a secondcategory of safety risk (e.g., “interpersonal behavior”), which can bedifferent than the first category of safety risk. The machine learningengine 230 determines 550 a safety score using a third classifier, e.g.,the ensemble classifier 450 shown in FIGS. 4A-B, based at least in parton the first and second safety sub-scores.

Determining safety scores for providers of the network system 100 usingtrained classifiers may be advantageous because the network system 100can save resources by automating the process instead of conductingmanual audits such as the crowdsourcing audit and internal auditpreviously described with reference to FIG. 3A. These systems alsoautomate a previously subjective process by evaluators; by permittinganalysis of particular sub-scores and learning relationships between thesub-scores and metadata, these systems provide an automated andeffective way to account for a wide variety of feedback and metadata.Further, at large-scale, the network system 100 could receive hundredsof thousands or even millions of feedback submissions from users, whichmay originate from various countries and in many languages from aroundthe world. Thus, it may be impractical or inefficient to manuallydetermine whether each feedback indicates a safe or unsafe provider.Further, by automating the classification and safety predictions, thenetwork system 100 can provide interventions to unsafe providers in realtime, e.g., during a service that an unsafe provider is providing to auser who submitted textual feedback.

Once the classifiers of the network system 100 learn to predict safetyrisk using a set of training data (e.g., feature vectors for differentcategories of safety risk and types of metadata), the classifiers maynot require additional manual user input. In some embodiments, themachine learning engine 230 can periodically re-train the classifierswith updated training data, for example, including a set of new textualfeedback and metadata received from user who received service fromproviders after the previous training of the classifiers. Furthermore,by characterizing metadata along with textual feedback during theclassifier training, the classifiers can more accurate predict safetyrisk, e.g., because the metadata provides context that may not beextracted from the textual feedback using natural language processingtechniques.

VI. Example Physical Components of a Computer

FIG. 6 is a high-level block diagram illustrating physical components ofa computer 600 used as part or all of the components from FIG. 1 (e.g.,the network system 100 or client devices 110), according to oneembodiment. Illustrated are at least one processor 602 coupled to achipset 604. Also coupled to the chipset 604 are a memory 606, a storagedevice 608, a graphics adapter 612, and a network adapter 616. A display618 is coupled to the graphics adapter 612. In one embodiment, thefunctionality of the chipset 604 is provided by a memory controller hub620 and an I/O controller hub 622. In another embodiment, the memory 606is coupled directly to the processor 602 instead of the chipset 604.

The storage device 608 is any non-transitory computer-readable storagemedium, such as a hard drive, compact disk read-only memory (CD-ROM),DVD, or a solid-state memory device. The memory 606 holds instructionsand data used by the processor 602. The graphics adapter 612 displaysimages and other information on the display 618. The network adapter 616couples the computer 600 to a local or wide area network.

As is known in the art, a computer 600 can have different and/or othercomponents than those shown in FIG. 6. In addition, the computer 600 canlack certain illustrated components. In one embodiment, a computer 600such as a server or smartphone may lack a graphics adapter 612, and/ordisplay 618, as well as a keyboard or pointing device. Moreover, thestorage device 608 can be local and/or remote from the computer 600,e.g., embodied within a storage area network (SAN).

As is known in the art, the computer 600 is adapted to execute computerprogram modules or engines for providing functionality described herein.As used herein, the terms “module” or “engine” refer to computer programlogic utilized to provide the specified functionality. Thus, a moduleand/or engine can be implemented in hardware, firmware, and/or software.In one embodiment, program modules and/or engines are stored on thestorage device 608, loaded into the memory 606, and executed by theprocessor 602.

VII. Additional Configurations

The foregoing description of the embodiments of the invention has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Some portions of this description describe the embodiments of theinvention in terms of algorithms and symbolic representations ofoperations on information. These algorithmic descriptions andrepresentations are commonly used by those skilled in the dataprocessing arts to convey the substance of their work effectively toothers skilled in the art. These operations, while describedfunctionally, computationally, or logically, are understood to beimplemented by computer programs or equivalent electrical circuits,microcode, or the like. Furthermore, it has also proven convenient attimes, to refer to these arrangements of operations as modules, withoutloss of generality. The described operations and their associatedmodules may be embodied in software, firmware, hardware, or anycombinations thereof.

Any of the steps, operations, or processes described herein may beperformed or implemented with one or more hardware or software modules,alone or in combination with other devices. In one embodiment, asoftware module is implemented with a computer program product includinga computer-readable non-transitory medium containing computer programcode, which can be executed by a computer processor for performing anyor all of the steps, operations, or processes described.

Embodiments of the invention may also relate to a product that isproduced by a computing process described herein. Such a product mayinclude information resulting from a computing process, where theinformation is stored on a non-transitory, tangible computer readablestorage medium and may include any embodiment of a computer programproduct or other data combination described herein.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the inventive subject matter.It is therefore intended that the scope of the invention be limited notby this detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsof the invention is intended to be illustrative, but not limiting, ofthe scope of the invention, which is set forth in the following claims.

1. A method comprising: receiving, from a client device of a user,textual feedback associated with a metadata and a provider, the textualfeedback including a plurality of words; determining a feature vectorfor the textual feedback by characterizing the plurality of words andthe metadata; determining a first safety sub-score by applying thefeature vector to a first classifier associated with a first category ofsafety risk, the first classifier being a machine learning model trainedusing a first training feature vector characterizing a first set oftextual feedback associated with the first category of safety risk;determining a second safety sub-score by applying the feature vector toa second classifier associated with a second category of safety riskdifferent than the first category of safety risk, the second classifierbeing a different machine learning model trained using a second trainingfeature vector characterizing a second set of textual feedbackassociated with the second category of safety risk; and determining asafety score for the provider using a third classifier based, at leastin part, on the first safety sub-score and the second safety sub-score.2. (canceled)
 3. The method of claim 1, further comprising: for eachword in the plurality of words: determining a first number ofoccurrences of the word in the plurality of words; and comparing thefirst number of occurrences to a second number of occurrences of theword in a plurality of reference texts; wherein the feature vector isfurther determined based on the comparisons.
 4. The method of claim 1,wherein the feature vector characterizes the plurality of words and themetadata using a plurality of dimensions associated with the pluralityof words and one or more dimensions associated with the metadata.
 5. Themethod of claim 1, further comprising: determining that the plurality ofwords includes one or more words semantically related to a word in theplurality of words; and determining a topic of the textual feedbackbased on the one or more word and the word, wherein the feature vectoris further determined based on the topic of the textual feedback.
 6. Themethod of claim 1, wherein the first category of safety risk isassociated with vehicle operation and wherein the second category ofsafety risk is associated with interpersonal behavior.
 7. The method ofclaim 1, wherein determining the safety score for the provider using thethird classifier is further based on a third safety sub-score determinedby a fourth classifier, the fourth classifier associated with themetadata.
 8. The method of claim 1, wherein the textual feedbackdescribes a transportation service provided by the provider for theuser, the metadata indicating at least one of a duration of thetransportation service or a distance of the transportation service. 9.The method of claim 8, wherein the metadata indicates at least one oftelematics data generated during transportation services previouslyprovided by the provider or an incident history of the provider based onthe transportation services previously provided.
 10. The method of claim1, wherein the metadata indicates at least one of a number of servicespreviously received by the user from providers of a network system or anincident history of the user based on the services previously received.11. A method comprising: receiving, from a client device of a user,textual feedback associated with a provider, the textual feedbackincluding a plurality of words; determining a feature vector for thetextual feedback by characterizing the plurality of words using aplurality of dimensions associated with the plurality of words;determining a first safety sub-score by applying the feature vector to afirst classifier associated with a first category of safety risk, thefirst classifier being a machine learning model trained using a firstset of training feature vectors characterizing a first set of textualfeedback associated with the first category of safety risk; determininga second safety sub-score by applying the feature vector to a secondclassifier associated with a second category of safety risk differentthan the first category of safety risk, the second classifier being adifferent machine learning model trained using a second set of trainingfeature vectors characterizing a second set of textual feedbackassociated with the second category of safety risk; and determining asafety score for the provider using a third classifier based, at leastin part, on the first safety sub-score and the second safety sub-score.12. The method of claim 11, further comprising: for each word in theplurality of words: determining a first number of occurrences of theword in the plurality of words; and comparing the first number ofoccurrences to a second number of occurrences of the word in a pluralityof reference texts; wherein the feature vector is further determinedbased on the comparisons.
 13. The method of claim 11, furthercomprising: determining that the plurality of words includes one or morewords semantically related to a word in the plurality of words; anddetermining a topic of the textual feedback based on the one or moreword and the word, wherein the feature vector is further determinedbased on the topic of the textual feedback.
 14. A computer programproduct comprising a non-transitory computer readable storage mediumhaving instructions encoded thereon that, when executed by one or moreprocessors, cause the one or more processors to: receive, from a clientdevice of a user, textual feedback associated with a metadata and aprovider, the textual feedback including a plurality of words; determinea feature vector for the textual feedback by characterizing theplurality of words and the metadata; determine a first safety sub-scoreby applying the feature vector to a first classifier associated with afirst category of safety risk, the first classifier being a machinelearning model trained using a first training feature vectorcharacterizing a first set of textual feedback associated with the firstcategory of safety risk; determine a second safety sub-score by applyingthe feature vector to a second classifier associated with a secondcategory of safety risk different than the first category of safetyrisk, the second classifier being a different machine learning modeltrained using a second training feature vector characterizing a secondset of textual feedback associated with the second category of safetyrisk; and determine a safety score for the provider using a thirdclassifier based, at least in part, on the first safety sub-score andthe second safety sub-score.
 15. The non-transitory computer readablestorage medium of claim 14, having further instructions that whenexecuted by the one or more processors cause the one or more processorsto: for each word in the plurality of words: determine a first number ofoccurrences of the word in the plurality of words; and compare the firstnumber of occurrences to a second number of occurrences of the word in aplurality of reference texts; wherein the feature vector is furtherdetermined based on the comparisons.
 16. The non-transitory computerreadable storage medium of claim 14, wherein the feature vectorcharacterizes the plurality of words and the metadata using a pluralityof dimensions associated with the plurality of words and one or moredimensions associated with the metadata.
 17. The non-transitory computerreadable storage medium of claim 14, having further instructions thatwhen executed by the one or more processors cause the one or moreprocessors to: determine that the plurality of words includes one ormore words semantically related to a word in the plurality of words; anddetermine a topic of the textual feedback based on the one or more wordand the word, wherein the feature vector is further determined based onthe topic of the textual feedback.
 18. The non-transitory computerreadable storage medium of claim 14, wherein determining the safetyscore for the provider using the third classifier is further based on athird safety sub-score determined by a fourth classifier, the fourthclassifier associated with the metadata.
 19. The non-transitory computerreadable storage medium of claim 14, wherein the textual feedbackdescribes a transportation service provided by the provider for theuser, the metadata indicating at least one of a duration of thetransportation service or a distance of the transportation service. 20.The non-transitory computer readable storage medium of claim 19, whereinthe metadata indicates at least one of telematics data generated duringtransportation services previously provided by the provider or anincident history of the provider based on the transportation servicespreviously provided.
 21. The method of claim 1, further comprising:sending a warning message to another client device of the providerresponsive to determining that the safety score is greater than athreshold value.